The distribution of perishable items, such as produce, as well as non-perishable products in thin, usually transparent, plastic bags have become widespread over the years. Plastic deformable bags have considerable strength and, further, have storage capabilities which enhance product quality and extend useful life. Mass production of these bags through automated machines have made them particularly desirable, feasible and cost effective. Typically, these assemblies pull a length of sheet plastic off a roll and fold the plastic back substantially over itself. The machine then cuts the sheet and heat seals each of the two sides proximate the edges of the sheet, thus forming a plastic bag. U.S. Pat. No. 4,590,747 to Schjeldahl is typical of these devices in which there is a cam driven apparatus having a film spreading and clamping assembly formed for folding the film and sealing it to form an open ended bag. Subsequently, the bag is aligned and positioned to be received by an assembly suitable for filling the bag.
Filling assemblies have been developed which mechanically grip a bag in a distended position and insert a product therein. Typical of such prior art bagging apparatus is U.S. Pat. No. 4,590,747 to Schjeldahl or U.S. Pat. No. 3,864,894 to Sheetz et al. One reoccurring problem results when one or both sides of the bag is not effectively sealed or the seam is defective. Thus, when the bag is positioned and received on the filling assembly, seams which are defective separate spilling the product through the gap.
Another problem occurs when a plastic bag is placed askew on the filling assembly. Because these packaging machines often operate at high speeds, an improperly or only partially gripped bag can slip off the machine and the product being bagged spilled or discharged into the machine. When the product is dropped, the machine can become jammed, requiring the machine to be stopped while the product is cleared. The resulting time delays greatly reduce the efficiency of the bagging machine and accordingly increase the costs of packaging.
As a result of these problems, machinery soon developed which mechanically sensed whether the deformable bag was properly placed on the bagging machine or not. Typical of these devices is the apparatus disclosed in U.S. Pat. No. 3,864,894 to Sheetz et al. This patent is directed to a bag assembly having means for clamping a deformable bag in place, holding it open during filling and thereafter transferring the bag into an automatic bag tier. The bag is clamped using two pairs of complimentary finger assemblies that approach the bag laterally. A single mechanical switch detects whether a bag is missing or is not clamped between the finger assemblies before filling. Upon detection of a malfunction, the device automatically shuts down preventing further misoperation of the device.
The Sheetz, et al. device, however, uses a mechanical micro-switch as a sensor and can only determine if a bag is clamped or not. This sensor does not detect the relative position of the bag with respect to the filling assembly (i.e., whether it is askew or whether it is pulled up high enough). Moreover, the sensor in Sheetz, et al. does not test the integrity of the bag seams.
Still, other sensing mechanisms have been employed in the packaging industry. U.S. Pat. No. 3,680,446, to James et al. discloses an apparatus and method relating to forming sheet materials into bags. Web edge alignment of rolled sheets of film is detected by a pressure sensing device comprising a stream of fluid (usually air) directed at a pressure sensor with the sheet material therebetween. When the sheet material is aligned, the material intercepts the stream and only static pressure is measured However, when the sheets become misaligned, the fluid stream is uninterrupted and the sensors detect the dynamic pressure. Subsequently, guide rollers adjust accordingly to realign the sheets.
The approach in the James, et al. patent depends on an extremely complex arrangement of shiftable rollers, shafts, adjustment cylinders, sensors and circuitry. The circuitry and apparatus in this device, however, only determine whether the sheet is misaligned two dimensionally. That is, whether the edge of the sheet material is misaligned to the left or right of the sensor. Moreover, the James, et al. device does not include sensors or circuitry which test the integrity of the material or seams of the bag.
Once the filling assemblies have properly performed their respective filling tasks, it usually is desirable to transfer the filled bag to an assembly which performs the function of sealing the bag. These sealing devices generally grip the bag proximate the upper open end, form a throat or neck and apply a closure device to secure the bag in a sealed condition. Typical of these devices are U.S. Pat. Nos. 1,738,511, 2,711,278, 2,916,863, 3,919,829, 3,922,834, 4,291,517 and 4,593,516. Heat sealing, in which the opposing edges of an open end bag are melted together forming a hermetic seal, also has been employed, for example, the apparatus as shown in U.S. Pat. No. 4,446,667 to Kokido.
Many of the sealing assemblies set forth above require manual transfer between the bag handling and bag sealing devices. This transfer, however, can be the source of serious problems. Bags can be dropped or the product damaged during the transfer. Accordingly, it is desirable to easily transfer the bag relatively undisturbed from the filling assembly to the sealing assembly. For example, U.S. Pat. No. 4,125,986 to Sheetz, et al. discloses a bagging assembly including a pivotal transfer arm which swings the filled bag into the throat of an automatic bag tying assembly. A pair of mechanical clamps mounted to the transfer arm continually grip the bag open as the arm pivots into the throat of the tying assembly.
The Sheetz, et al. device, however, is not adaptable to filling assemblies which insert portions of the filling device into the bag, which can be required for bagging certain products, such as leafy produce. Additionally, the gripping and transfer arm mechanism in the Sheetz, et al. patent does not itself remove the bag from the filling assembly. The bag edge is continually gripped and the assembly never relinquishes hold of the bag during the filling and sealing cycle. Moreover, the pivotal nature of the transfer arm prevents transfer of the bag to the sealing assembly unless the filling assembly is completely removed from the bag.
Other transferring assemblies include movable carriage-type devices, such as U.S. Pat. No. 4,291,517 to Lipes. This reference provides a tab structure attached proximate the upper open end portion of the bag which is, in turn, slidably coupled to holding pins suitable for guiding the bag along tracks into engagement with a tying mechanism. This structure as a whole is nonadjustable and severe problems occur when a product interferes with the guiding tracts.
Finally, some bagging assemblies employ conveyor belt systems coupled between the filling assembly and the sealing assembly. U.S. Pat. No. 3,919,829 to Buford et al. and U.S. Pat. No. 2,513,459 to Dodge disclose such mechanisms. These devices, however, do not positively control the flexible open edges proximate the upper portion of the bag. Because of the flexible nature of the bag, if the open edges are not clear of the inserter, the edges will be smashed down and the product improperly inserted. Furthermore, when the bag is finally transferred to the sealing assembly, via the conveyor belt, bags having wrinkled or folded edges will not be properly positioned for engagement with the tying assembly resulting in bag sealing aberrations.
In commercial practice, the prior assemblies have been satisfactory for many applications. However, it is highly desirable to provide a bagging assembly and method capable of pneumatically detecting the position an condition of a deformable bag with respect to the bag filling assembly. Moreover, it is further desirable to provide an assembly and method capable of transferring the filled deformable bag from the filling assembly to the sealing assembly while maintaining positive control of the open end edges of the bag.
Accordingly, a primary object of the present invention is to provide a bag filling apparatus and method which permits the bagging of a product and sealing of the bag automatically without commercially unacceptable damage to the product.
It is another object of the present invention to provide an apparatus and method which increases packaging and production efficiency.
Still another object of the present invention is to provide a bag filling apparatus and method which will detect when a bag seam is not properly sealed.
Still a further object of the present invention is to provide an apparatus and method which will detect when a bag has been improperly gripped by the filling apparatus or is askew.
It is yet another object of the present invention to provide a bag filling apparatus and method which will warn the operator of the malfunction so that the bag can be either adjusted on the machine or removed and a new bag put in its place.
It is still another object of the present invention to provide a bag filling apparatus and method which will grippably remove the deformable bag from the filling apparatus while maintaining positive control of the bag edges and transfer it to the sealing apparatus.
It is a further object of the present invention to provide a bag filling apparatus and method which is durable, compact, easy to maintain, has a minimum number of components and is economical to manufacture.
The apparatus of the present invention has other objects and features of advantage which will become apparent from and are set forth in more detail in the description of the Best Mode of Carrying Out the Invention and the accompanying drawing.